Long Term Evolution (LTE)/LTE-Advances (LTE-A) as the 3GPP mobile communication stand provides the high speed packet service based on Orthogonal Frequency Division Multiplexing (OFDM).
FIG. 1 is a diagram illustrating the 3GPP system architecture according to the convention technology. FIG. 1 shows an exemplary structure of the LTE/LTE-A wireless mobile communication system to be referenced in the present invention.
Referring to FIG. 1, the radio access network of the LTE mobile communication system includes evolved Node Bs (eNBs) 105, 110, 115, and 120), Mobility Management Entity (MME) 125, and Serving-Gateway (S-GW) 130. The User Equipment (UE) 135 connects to an external network via the eNB and S-GW. The eNBs 105 to 120 correspond to the legacy node Bs of the UMTS system. The UE 135 connects to the eNB is connected with the UE 135 through a radio channel and responsible for complicated functions as compared to the legacy node B. In LTE, all the user traffic including real time services such as Voice over Internet Protocol (VoIP) are provided through a shared channel and thus there is a need of a device for scheduling data based on the UE state information such as eNBs 105 to 120. Typically, one eNB controls a plurality of cells.
In order to secure the data rate of up to 100 Mbps, the LTE system adopts Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in the bandwidth of up to 20 Mhz. Also, the LTE system adopts Adaptive Modulation and Coding (AMC) to determine the modulation scheme and channel coding rate in adaptation to the channel condition of the UE. The S-GW 130 is an entity to provide data bearers so as to establish and release data bearers under the control of the MME 125. MME 125 is responsible for various control functions and connected to a plurality of eNBs.
According to the current 3GPP standard TS36.304 UE procedures in idle mode Protocol and TS36.331 Radio Resource Control Protocol, the UE estimates the UE mobility state by comparing a number of cell reselections (applied to the UE in idle mode) or a number of handovers (applied to the UE in connected mode) in a predetermined timer duration.
In the 3GPP standard TS36.304 UE procedures in idle mode Protocol, the mobility state of the UE is classified into one of three states and the eNB signals two sets of timer values and the threshold value to be compared with the number of cell selections or handovers.
In the Heterogeneous Network (HetNet) scenario in which a plurality cells having various sizes are deployed, however, cell reselection or handover may occurs to the cell having various cell sizes with the same or similar geographical area. Furthermore, since the plural cells having various cell sizes may not be installed by the operator, it may be difficult for the eNB to configure the timer values and the threshold value to be compared with the number of cell reselections or handovers for estimating the mobility state of the UE accurately.